| Re: Failed to write to a text file (text file is RW) [message #171419 is a reply to message #171416] |
Sun, 02 January 2011 22:13   |
Jerry Stuckle
Messages: 2598
Registered: September 2010
Karma:
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Senior Member |
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On 1/2/2011 4:07 PM, justaguy wrote:
> On Jan 2, 3:35 pm, Jerry Stuckle<jstuck...@attglobal.net> wrote:
>> On 1/2/2011 3:19 PM, justaguy wrote:
>>
>>
>>
>>> Hi,
>>
>>> I dig up the following script. Added a simple HTML file with a form
>>> field named "vote" and have it send to the following php script.
>>> However, it failed to write to the poll_result.txt file. Why?
>>
>>> Thanks as usual.
>>
>>> <?php
>>> $vote = $_REQUEST['vote'];
>>
>>> //get content of textfile
>>> $filename = "poll_result.txt";
>>> $content = file($filename);
>>
>>> //put content in array
>>> $array = explode("||", $content[0]);
>>> $yes = $array[0];
>>> $no = $array[1];
>>
>>> if ($vote == 1)
>>> {
>>> $yes = $yes + 1;
>>> }
>>> if ($vote == 0)
>>> {
>>> $no = $no + 1;
>>> }
>>
>>> // debug
>>> echo $yes;
>>> echo $no;
>>
>>> // output and comments
>>> /*
>>> Seed poll_result.txt to read 0||0
>>
>>> It's always 10 even though I checked the YES option several times
>>> obviously it failed to write to the poll_result.txt file.
>>
>>> Checked the poll_result.txt, it's 0||0
>>
>>> */
>>
>>> //insert votes to txt file
>>> $insertvote = $yes."||".$no;
>>> $fp = fopen($filename,"w");
>>> fputs($fp,$insertvote);
>>> fclose($fp);
>>> ?>
>>
>> Are you sure you're looking at the same file you're writing to? You're
>> using a relative path, after all (which would place the data file in
>> your web path, where it could be downloaded by anyone - not a good idea).
>>
>> Does the user (if this is running under the web server, the web server
>> user) have permission to write to the file?
>>
>> And finally, this is totally unsafe. There is nothing stopping two
>> different people from opening the file at the same time, potentially
>> corrupting your date.
>>
>> --
>> ==================
>> Remove the "x" from my email address
>> Jerry Stuckle
>> JDS Computer Training Corp.
>> jstuck...@attglobal.net
>> ==================
>
> Well, on "where it could be downloaded by anyone", how come? The
> processPoll.php file or a similar process php script is a server
> script,
> average user can't mess up with it.
>
That's fine - but the data file itself is in the same directory - where
a knowledgeable user has direct access to it.
> On file permission, sorry, I forgot to mention, it's Read and Write.
> A similar php script executes fine.
>
read/write for whom?
> On your last point of " this is totally unsafe. There is nothing
> stopping two
>> different people from opening the file at the same time, potentially
>> corrupting your date."
> Once we fix the above two problems what could we do about it? I'm
> totally new to php btw.
>
> Many thanks.
>
>
Has nothing to do with PHP - this can occur in ANY language. You need
to learn all about how to work in a multitasking environment. Basically,
you have to limit access to the file so that only one script can access
it at a time. How you do it is dependent on the OS.
Or you can use a database which is built for multitasking (most are).
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex(at)attglobal(dot)net
==================
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